50 lines
3.4 KiB
Markdown
50 lines
3.4 KiB
Markdown
# ludic.anim
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The animation clips an animator keyed into a glTF, played on a render3d `Skin` and cross-faded two
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at a time. `ludic.render3d` parses no animations and offers a pose api (`skin_set_quat`,
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`skin_set_offset`, `skin_pose`) rather than a player, so the sampler lives here. Uses
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`ludic_render3d` and nothing else: it reads the document `gltf_load` just parsed and writes a
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Skin's pose. It asks the game nothing, so it has no port.
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```ludic
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import "ludic.anim"
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let m = gltf_load("assets/kit/hiker2", "hiker_m.gltf", "hiker_m")
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anim_read_doc("assets/kit/hiker2") # straight after the load, before the next
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let walk = anim_find("hiker_m_walk")
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anim_play(sk, walk, t, idle, t2, 0.3) # 70% walk, 30% idle, into the joint matrices
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```
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## API
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| --- | --- |
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| `Clip { name, dur, n, cnode, cpath, ckeys, coff, cvoff, times, vals }`, `AC_ROT`, `AC_POS` | a clip, its channels flattened: a channel's keys are `times[coff..coff+ckeys]`, its values 4 (rotation) or 3 (translation) per key from `cvoff` |
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| `anim_read_doc(dir) -> int` | every rotation and translation channel of every animation in `gltf_doc`, reading the `.bin` beside it in `dir`; how many clips were new |
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| `anim_find(name) -> Clip`, `anim_count()`, `anim_add(c) -> bool`, `anim_clear()` | the table, by name; a name already held is skipped on read and refused on add |
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| `anim_play(sk, a, ta, b, tb, blend) -> bool` | `a` at `ta`, cross-faded toward `b` at `tb` by `blend` (0 all a, 1 all b; `b` may be null), folded into the joint matrices |
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| `anim_mix(c, sk, t, w, rot, pos, hit)`, `anim_to_pose(sk, rot, pos, hit)`, `anim_key_at(c, ch, t)` | the pieces `anim_play` is made of, for a caller that mixes more than two |
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| `anim_set_positions(on)`, `anim_positions()` | keyed translations applied or not (off: baking keys location on every bone, and rounding down an eighteen-bone chain is a collapsed animal) |
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| `skin_joint(sk, name)`, `skin_joint_quiet(sk, name)` | a bone by name in the skin's OWN joints: a kit packs several rigs with the same bone names, and render3d's `skin_find` answers the file's first, which belongs to another rig (the pose is then stored and never drawn) |
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| `anim_first_key(c) -> float` | the earliest key; a read warns when it is not zero |
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## Rules it keeps
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- **Clips are named per rig.** A channel addresses its FILE's node indices, two files number their
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nodes differently, and a name already held is skipped - so one shared name would hand the
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second body the first one's skeleton. Name them `hiker_m_walk` / `hiker_f_walk`, `bear_walk`.
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- **Read straight after the load.** `gltf_doc` is whichever file was parsed last, and `gltf_load`
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closes the `.bin`, which `anim_read_doc` reopens (a read through the closed handle is zeros).
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- **Key from frame zero.** A clip wraps on its duration and holds below its first key, so a clip
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keyed from frame 1 holds its opening pose for 1/30 s every cycle. `anim_read_doc` prints it.
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- **The math.** `skin_pose` takes a delta D in the model frame, `local = (G_p^-1 D G_p) R_rest`,
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and a channel gives the absolute local L, so D = G_p (L R_rest^-1) G_p^-1.
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- The scratch is made once and grown: a call is per actor per frame.
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## Tests
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```bash
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ludic test packages/ludic.anim
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```
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A two-bone skin made from a glTF document with no GPU: sampling, wrapping, the cross-fade,
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translations off by default, and clips read out of a `.bin` written to the temp directory.
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